When Ice Block is active, casting it again will cancel it.
Ice Block can be removed by an enemy's [Mass Dispel].
Ice Block can be used while afflicted by loss of control effects such as stuns or fear effects.
Ice Block can prevent fall damage. It can also prevent damage from drowning and fatigue, but it will not reset the breath bar or the fatigue bar, so as soon as the block ends the damage will continue.
Since mobs will not attack immune targets, Ice Block causes them to ignore the caster for its duration. It does not reduce threat levels.
A stopcasting macro can be used to make Ice Block more responsive, by having it immediately stop any in-progress spellcasts when its button is pressed:
"Improved Ice Block" is one of Jaina's abilities in Heroes of the Storm. It functions similarly to Ice Block, but with the added effect of chilling nearby enemies when it ends.
Patch 5.0.4 (2012-08-28): Now learned at level 26 (was 30).
Patch 2.3.2 (2008-01-08): Ice Block is no longer a talent, and is now trainable at level 30 (was a tier 5 Frost talent).
Patch 2.3.0 (2007-11-13): Ice Block has been reverted back to its old behavior.
Originally, a player who Ice Blocked in midair would continue to fall normally. At one point this was changed so an Ice Blocked player hovered while the spell was active, then began to fall when it expired.